It is known to prepare an aqueous solution of dichlorohydrin e.g., 2,3 dichloro-1-propanol and 1,3 dichloro-1-propanol, herein collectively dichlorohydrin, by reacting in a reaction zone allyl chloride, water and chlorine in dilute aqueous phase.
U.S. Pat. No. 2,714,121, incorporated herein by reference, discloses producing halohydrins by using high dilution of e.g. 250 to 400 volumes of water per volume of e.g., a halosubstituted hydrocarbon in aqueous medium with subsequent addition of the halogen, and keeping the organic by-product phase dispersed as fine particles.
U.S. Pat. No. 2,714,123, incorporated herein by reference, discloses producing an aqueous solution of dichlorohydrin in a series of reaction zones wherein substantially all of the water is fed to the first of the reaction zones and the other reactants added in substantially equimolar proportions into each of the other reaction zones.
U.S. Pat. No. 3,909,382 discloses recovering acid values, such as hydrochloric acid formed during olefin chlorohydrination, by series flow through a plurality of electrodialysis stages to upgrade the acid to higher concentration.
Japanese Pat. No. 74,00369 relates that the product mixture from the reaction of a lower olefin, chlorine and water can be electrodialyzed to remove the by-produce ions of hydrogen and chlorine, and the ion-depleted chlorohydrin solution circulated to the single reaction zone, enabling the production of a concentrated aqueous chlorohydrin solution.
As disclosed in copending application Ser. No. 814,331 (K-2317), filed Dec. 27, 1985, in a multistage dichlorohydrin production system, increased selectivity to the desired dichlorohydrin may be obtained by electrodialyzing the reaction effluent of one stage prior to being fed to a subsequent stage.
A disadvantage of e.g., the process in said copending application Ser. No. 814,331 (K-2317) filed Dec. 27, 1985 is that removal of the ions requires substantial electrodialysis membrane area, adding to the capital cost required to achieve the desired selectivity.
It has now been found that advantageous selectivity can be retained by employing an electrodialysis unit in parallel flow to at least one reaction stage to remove a substantial part of the acid from the reaction mixture into a concentrate stream, and neutralizing said acid in said concentrate stream.